Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
255 PM EST Wed Feb 21 2018
Valid 00Z Thu Feb 22 2018 - 00Z Sat Feb 24 2018
...Cold and unsettled weather is expected over the West including
some heavy snow over the Rockies...
...Additional heavy rainfall and widespread concerns for flooding
will persist across parts of the southern Plains, lower
Mississippi Valley and the Ohio Valley...
...Warm temperatures are generally expected to continue across a
large portion of the East...
The Western U.S. will mainly be cold, but also unsettled through
the end of the week, as a series of impulses dropping south across
western North America help to reinforce a broad upper level trough
of low pressure. This will maintain below normal temperatures with
most of the West seeing high temperatures about 10 to 20 degrees
below normal. This energy will also bring the threat for heavy
snow across parts of northern California, the Great Basin and the
central Rockies as the energy traverses the interior of the West.
Unfortunately, these impulses of energy ejecting down across the
West and then out into the Plains will be the primary drivers of
multiple rounds of heavy rainfall farther off to the east. This
will include portions of the southern Plains, lower Mississippi
Valley and Ohio Valley as multiple waves of low pressure eject
northeast up along a frontal zone draped across the region. This
additional rainfall will be largely falling on saturated ground
from recent heavy rain over the last several days and going back
to last week in some cases. Therefore, the threat for additional
flash flooding and main stem river flooding will become enhanced
through the remainder of the week.
Aside from the focus for heavy rainfall, the same aforementioned
front is marking the difference from an abnormally warm airmass in
place across much of the East where temperatures are reaching as
high as the 70s and 80s, and a very cold airmass that has nosed
south down across much of the Plains where temperatures are
locally below freezing as much as 10 to 20 degrees below normal.
Over the next couple of days, some of the warm air across
especially the Northeast and parts of the Mid-Atlantic region will
be tempered by a modestly colder airmass behind a frontal passage
later tonight, but this boundary will stall out from the lower
Mississippi Valley to across the Tennessee Valley and into the
Mid-Atlantic region on Thursday before then gradually beginning to
lift back north as a warm front by Friday as a new area of low
pressure lifts up across the Midwest. This will keep the Southeast
U.S. in particular quite warm with much above normal temperatures
through the end of the week.
Regarding the threat of winter weather, there will be the approach
of a wave of low pressure from the Tennessee Valley on Thursday
that will actually interact with sufficient cold air over parts of
the upper Ohio Valley, far northern Mid-Atlantic and interior of
the Northeast for a stripe of some accumulating snow and ice.
Meanwhile, there will also be a swath of accumulating snow and ice
across portions of especially the central Plains, Midwest and
Great Lakes for Thursday and Friday as low pressure rides
northeast up across the region.
Orrison
Graphics available at
www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
942 AM EST WED FEB 21 2018
VALID 12Z SAT FEB 24 2018 - 12Z WED FEB 28 2018
DUE TO TECHNICAL DIFFICULTIES, SOME PRODUCTS MAY NOT BE AVAILABLE
OR UPDATED. PLEASE CHECK ISSUANCE TIMES. WE APOLOGIZE FOR ANY
INCONVENIENCE.
...PATTERN OVERVIEW...
MOST GUIDANCE MAINTAINS AN AMPLIFIED MEAN PATTERN CONSISTING OF
SHORTWAVES PERIODICALLY DIGGING INTO A WEST COAST/INTERIOR WEST
MEAN TROUGH AND THEN EJECTING AROUND A DOWNSTREAM RIDGE WHOSE
SHAPE WILL EVOLVE WITH TIME. THE MOST COMMON SCENARIO AMONG
LARGEST GUIDANCE IS FOR A LEADING SHORTWAVE EJECTING FROM THE
ROCKIES/HIGH PLAINS AROUND THE START OF THE WEEKEND TO GENERATE A
POTENTIALLY MAJOR STORM REACHING THE GREAT LAKES BY SAT
NIGHT/EARLY SUN, FOLLOWED BY A FAIRLY WEAK/DIFFUSE AND PROGRESSIVE
SHORTWAVE, AND FINALLY DEEPER WESTERN TROUGH AMPLIFICATION NEXT
MON-WED. THIS EVOLUTION/PROGRESSION WILL MOST LIKELY LEAD TO
STEADY EROSION OF INITIALLY STRONG RIDGING ALONG/OFFSHORE THE EAST
COAST FOLLOWED BY A SHIFT OF RIDGE EMPHASIS INTO THE GULF OF
MEXICO AND THEN SOME REBUILDING OF A RIDGE OVER THE EAST-CENTRAL
U.S. BY MIDWEEK AS WESTERN TROUGHING AMPLIFIES.
...MODEL GUIDANCE/UNCERTAINTY ASSESSMENT/PREFERENCES...
ONE SIGNIFICANT FOCUS OF THE FORECAST WILL BE ON THE STORM SYSTEM
ASSOCIATED WITH THE SHORTWAVE EMERGING FROM THE ROCKIES/HIGH
PLAINS AT THE START OF THE PERIOD EARLY SAT. THERE IS STILL A
MODERATE AMOUNT OF SPREAD FOR EXACTLY HOW THIS SYSTEM WILL EVOLVE
BUT MOST MODEL/ENSEMBLE SOLUTIONS HAVE TRENDED NOTICEABLY DEEPER
VERSUS 24 HOURS AGO, WHILE THE GFS CONTINUES TO BE THE DEEPEST
MODEL. THIS DEEPER TREND WOULD MERIT SOME INCORPORATION OF THE
00Z/06Z GFS SCENARIO INTO THE FORECAST AS PART OF A MODEL
COMPROMISE BUT OCCASIONALLY DEEP BIASES STILL LEAVE SOME LINGERING
DOUBT IN GOING AS DEEP AS THE GFS. THERE ARE STILL INDICATIONS
THAT A WEAK WAVE WILL FORM OFF THE NORTHEAST COAST AS THE PARENT
LOW TRACKS OVER SOUTHEAST CANADA. SPECIFICS OF THIS WAVE WILL
PLAY AN IMPORTANT ROLE IN HOW LONG COOL AIR REMAINS OVER NEW
ENGLAND.
THERE IS DECENT CONTINUITY FROM YESTERDAY THAT A TRAILING
SHORTWAVE REACHING THE NORTHWEST DURING THE WEEKEND SHOULD BE
FAIRLY WEAK AND PROGRESSIVE, WITH AT MOST A MODEST SURFACE
REFLECTION AS THE FEATURE CONTINUES ACROSS LOWER 48.
THE OTHER MEANINGFUL UNCERTAINTY IN TODAY'S FORECAST INVOLVES
EASTERN PACIFIC/WESTERN U.S. EVOLUTION TOWARD THE LATTER HALF OF
THE PERIOD, WITH MODELS AND TO A GREATER EXTENT INDIVIDUAL
ENSEMBLE MEMBERS DISPLAYING BROADENING SPREAD FOR COMBINED
EVOLUTION OF TROUGH ENERGY DIGGING INTO THE WEST AND
UPSTREAM/INFLUENCING ENERGY REACHING THE NORTHEAST PACIFIC. BEST
MODEL/MEAN CONSENSUS (ECMWF/CMC AND GEFS/ECMWF/CMC MEANS) HAS A
FAIRLY SHARP AND DEEP UPPER TROUGH REACHING JUST INLAND FROM THE
WEST COAST BY DAYS 6-7 TUE-WED, WITH INDICATIONS THAT THERE COULD
BE AN EMBEDDED CLOSED LOW. THIS MAJORITY SOLUTION IS A LITTLE
FASTER THAN THE 00Z GFS BUT SLOWER THAN THE 06Z RUN.
...WEATHER HIGHLIGHTS/THREATS...
THE DEEPENING STORM SYSTEM TRACKING FROM NEAR THE CENTRAL PLAINS
THROUGH THE GREAT LAKES INTO SOUTHEAST CANADA DURING THE WEEKEND
WILL BRING A BROAD AREA OF ACTIVE WEATHER TO THE CENTRAL AND
EASTERN U.S. AHEAD OF THE FRONT TRAILING FROM THE SURFACE LOW,
EXPECT AREAS OF HEAVY RAINFALL INCLUDING OVER PORTIONS OF THE
MS/OH VALLEY REGION THAT HAS ALREADY EXPERIENCED
CONSIDERABLE/EXCESSIVE RAINFALL. THUS FLOODING CONCERNS WILL
CONTINUE. SOME CONVECTION MAY ALSO BE STRONG TO SEVERE WITH SPC
CURRENTLY HIGHLIGHTING SUCH POTENTIAL FROM EXTREME NORTHEAST TX
INTO WESTERN TN AND VICINITY. CONSULT LATEST SPC OUTLOOKS FOR
LATEST INFO. MEANWHILE BEST POTENTIAL FOR COLD SECTOR SNOW WILL
EXTEND FROM THE NORTH-CENTRAL PLAINS THROUGH THE UPPER MS
VALLEY/UPPER GREAT LAKES AND INTO NEW ENGLAND, WITH A TRANSITION
ZONE/CHANGEOVER POSSIBLE BETWEEN THE SNOW AND RAIN AREAS. STRONG
WINDS MAY ALSO BECOME A CONCERN DEPENDING ON HOW THE SYSTEM
DEVELOPS. AFTER SYSTEM PASSAGE RAINFALL OF VARYING INTENSITY MAY
LINGER FOR A TIME OVER THE SOUTHERN TIER/SOUTHERN MID ATLANTIC.
OVER THE WEST, INITIALLY EXPECT SOME COASTAL/LOW ELEVATION RAIN
AND OTHERWISE SNOW FROM THE PACIFIC NORTHWEST/NORTHERN ROCKIES
INTO THE GREAT BASIN/SOUTH-CENTRAL ROCKIES FOLLOWED BY ANOTHER
PERIOD OF PRECIP THAT SHOULD EVENTUALLY PUSH SOUTHWARD FROM
NORTHERN AREAS INTO THE GREAT BASIN AND CA. GUIDANCE SPREAD FOR
DETAILS ALOFT IS STILL SUFFICIENTLY HIGH TO TEMPER CONFIDENCE IN
DETERMINING COVERAGE AND INTENSITY OF ACTIVITY OVER CA/GREAT
BASIN. HOWEVER THERE IS ENOUGH AGREEMENT IN PRINCIPLE THAT UPPER
TROUGH DEPTH MAY SUPPORT FAIRLY LOW SNOW LEVELS OVER SOME AREAS BY
NEXT MON-WED.
THE AMPLIFIED PATTERN WILL MAINTAIN A SHARP CONTRAST IN
TEMPERATURE ANOMALIES OVER THE LOWER 48. DURING THE WEEKEND SOME
AREAS IN THE EAST MAY SEE MINS OF 20-30F ABOVE NORMAL FOR
POTENTIAL DAILY RECORDS AND DAYTIME HIGHS 15-20F ABOVE NORMAL.
LESS EXTREME WARM ANOMALIES SHOULD PERSIST OVER THE EAST INTO NEXT
WEEK. ON THE OTHER HAND MUCH OF THE WEST INTO THE NORTHERN PLAINS
SHOULD REMAIN WELL BELOW NORMAL DURING THE FORECAST PERIOD. THE
NORTHERN HIGH PLAINS SHOULD BE COLDEST WITH MAX TEMPS AVERAGING
15-20F BELOW NORMAL BUT MANY OTHER LOCATIONS OVER THE
WEST/NORTHERN PLAINS SHOULD SEE ONE OR MORE DAYS WITH MIN AND/OR
MAX TEMPS AT LEAST 10F BELOW NORMAL AS WELL.
RAUSCH

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
416 PM EST WED FEB 21 2018
VALID 00Z THU FEB 22 2018 - 00Z SUN FEB 25 2018
DAYS 1-3...
LINGERING TECHNICAL DIFFICULTIES CAUSED A LIMIT OF OPTIONS FOR
THERMAL FIELDS IN WWD SNOW TO THE 12Z OPERATIONAL GFS AND NAM.
THESE WERE IN FAIRLY GOOD AGREEMENT EXCEPT FOR SURFACE
TEMPERATURES AND ASSOCIATED ICE ISSUES IN THE NORTHEAST ON DAY 2
WHICH IS NOTED BELOW.
...CENTRAL ROCKIES ACROSS PLAINS TO MIDWEST...
A SHORTWAVE TROUGH EJECTS NORTHEAST FROM THE DESERT SOUTHWEST
TONIGHT. DEEP MOISTURE FROM A PLUME CONNECTED TO THE TROPICAL EAST
PACIFIC ALLOWS DECENT SNOW TO SOUTHERN CO TONIGHT WHERE SOUTHERLY
850MB FLOW BRINGS IN 0.25IN PW.
MEANWHILE...A LOW LEVEL INVERTED TROUGH DEVELOPS FROM SOUTH TO
NORTH UP THE GREAT PLAINS FROM OK TO IA WITH A WINTRY MIX EXPECTED
GIVEN THE SHALLOW COLD AIR IN PLACE AT THE SURFACE. FREEZING RAIN
IS THE PREFERRED P-TYPE WHERE THE 850MB TEMP GETS ABOVE 0C. RISK
FOR A TENTH INCH OF ICE THROUGH MAIN CORE OF THIS TROUGH PRIMARILY
FROM CENTRAL OK TO CENTRAL IA THROUGH THURSDAY. SOUTHERLY LOW
LEVEL FLOW IS ENHANCED AHEAD OF THE EJECTING SHORTWAVE FROM THE
SOUTHWEST...SETTING UP A RAIN TO FREEZING RAIN TO SLEET TO SNOW
PATTERN ACROSS THE MID-CONUS BOTH TONIGHT AND THURSDAY.
ALSO...LOW LEVEL SOUTHERLY FLOW OVERRUNNING OVER THE SURFACE COLD
FRONT OVER THE MIDWEST WILL ALSO LEAD TO A SWATH OF FREEZING RAIN
CENTERED OVER NORTHERN OH WHERE A TENTH INCH ACCUM IS LIKELY
TONIGHT.
A STRONGER WAVE IN THE WESTERN TROUGH EJECTS NORTHEAST FROM THE
DESERT SOUTHWEST FRIDAY NIGHT. SURFACE LOW DEVELOPMENT IS EXPECTED
NEAR THE EASTERN CO/NM BORDER WITH A TRACK TO THE UP SATURDAY
NIGHT. GULF MOISTURE IS TAPPED INTO AN WRAPPED AROUND THE SYSTEM
INTO A DEVELOPING DEFORMATION ZONE LATE FRIDAY NIGHT MEANING THE
SOUTHWESTERN GREAT PLAINS WHICH ARE FACING QUITE A DROUGHT LOOK TO
REMAIN DRY DESPITE A SURFACE LOW PASSAGE OVERHEAD. IN FACT...MOST
OF THE HEAVY SNOW LATE ON DAY 2 IS OVER UT AND WESTERN CO...WEST
OF THE CONTINENTAL DIVIDE.
A SWATH OF HEAVY SNOW IS LIKELY TO FORM ALONG THE NORTH SIDE OF
THE LOW STARTING IN NEBRASKA. AS DAY 3 ENDS AT 00Z SATURDAY THIS
IS AT THE END OF THE WWD FORECAST PERIOD...BUT AS OF NOW THE 12Z
GFS MAINTAINS THAT HEAVY SWATH ACROSS MN AS THE LOW CENTER
APPROACHES THE UP. STRENGTH AND TRACK UNCERTAINTY IS PARTICULARLY
HIGH IN THIS SUITE OF PRODUCTS GIVEN THE LACK OF FOREIGN MODEL
AVAILABILITY.
...NORTHEAST...
OVERRUNNING GULF AND TROPICAL PACIFIC MOISTURE OVER THE COLD FRONT
WILL GREAT A WINTRY MIX SWATH FROM NORTHERN OH/PA/NY TO SOUTHERN
NEW ENGLAND THURSDAY. RATHER MILD AIR IS CURRENTLY ACROSS THIS
AREA...BUT THE COLD FRONT WILL MOVE THROUGH TONIGHT...ALLOWING
COLD AIR TO BE IN PLACE BY THURSDAY. A QUICK TRANSITION FROM RAIN
TO FREEZING RAIN TO SLEET TO SNOW WILL TAKE PLACE ALONG THIS
FRONT. THE SWATH OF HEAVY OVERRUNNING SNOW ALONG THE PA/NY BORDER
INTO NY.
A SECOND SWATH OF WINTRY MIX CROSSES THE ENTIRE NORTHEAST FRIDAY
AS A SHORTWAVE TRACKS OVER THE NORTHERN GREAT LAKES WITH CONTINUED
SOUTHERLY FLOW OVER THE SURFACE COLD AIR. THE 1040MB HIGH SHIFTS
EAST FROM NORTHERN NEW ENGLAND THURSDAY NIGHT WITH A COLD AIR
DAMMING WEDGE EXPECTED TO PERSIST BACK ACROSS THE NORTHERN
MID-ATLANTIC. MODELS ARE NOTORIOUS FOR ERODING COLD AIR
PREMATURELY ON WINTER NIGHTS WITH SOUTHERLY FLOW. ATTEMPTED TO
BLEND THE COLDER/ICIER 12Z NAM WITH THE WARMER 12Z GFS.
ACCUMULATING SNOW LOOKS LIMITED IN THE NORTHEAST DAY 2/3 TO
NORTHERN MAINE FRIDAY EVENING.
...PACIFIC NORTHWEST TO GREAT BASIN...
A STRONG SHORTWAVE TROUGH DROPS SOUTH FROM THE PAC NW THIS
EVENING. HOWEVER...PACIFIC MOISTURE WILL BE CONTAINED OFFSHORE
FROM NORTH WINDS. THEREFORE...LIGHT TO LOCALLY MODERATE SNOWS ARE
EXPECTED ACROSS OR/SOUTHERN ID/NORTHERN NV/AND HIGHER ELEVATIONS
OF NORTHERN CA. OF NOTE IS THE LOWERING HEIGHTS WHICH WILL ALLOW
INTERIOR VALLEYS IN OR TO RECEIVE A SECOND ROUND OF SNOW THIS
WEEK...INCLUDING PORTLAND WHERE AROUND AN INCH IS FORECAST.
A SECOND TROUGH WILL PUSH SOUTHEAST INTO THE PAC NW LATE FRIDAY
INTO SATURDAY. NORTHWESTERLY ONSHORE FLOW WILL ALLOW MUCH HEAVIER
PRECIPITATION THAN THE PREVIOUS SHORTWAVE WITH HEAVY SNOW EXPECTED
IN THE HIGHER ELEVATIONS AND LOWERING HEIGHTS AGAIN CAUSING VERY
LOW SNOW ELEVATIONS POTENTIALLY IMPACTING SEATTLE AND PORTLAND
FRIDAY NIGHT.
THE PROBABILITY FOR IMPACTFUL ICING IS LOW ACROSS THIS AREA
THROUGH THE FORECAST PERIOD.
JACKSON

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
942 AM EST WED FEB 21 2018
VALID 12Z SAT FEB 24 2018 - 12Z WED FEB 28 2018
DUE TO TECHNICAL DIFFICULTIES, SOME PRODUCTS MAY NOT BE AVAILABLE
OR UPDATED. PLEASE CHECK ISSUANCE TIMES. WE APOLOGIZE FOR ANY
INCONVENIENCE.
...PATTERN OVERVIEW...
MOST GUIDANCE MAINTAINS AN AMPLIFIED MEAN PATTERN CONSISTING OF
SHORTWAVES PERIODICALLY DIGGING INTO A WEST COAST/INTERIOR WEST
MEAN TROUGH AND THEN EJECTING AROUND A DOWNSTREAM RIDGE WHOSE
SHAPE WILL EVOLVE WITH TIME. THE MOST COMMON SCENARIO AMONG
LARGEST GUIDANCE IS FOR A LEADING SHORTWAVE EJECTING FROM THE
ROCKIES/HIGH PLAINS AROUND THE START OF THE WEEKEND TO GENERATE A
POTENTIALLY MAJOR STORM REACHING THE GREAT LAKES BY SAT
NIGHT/EARLY SUN, FOLLOWED BY A FAIRLY WEAK/DIFFUSE AND PROGRESSIVE
SHORTWAVE, AND FINALLY DEEPER WESTERN TROUGH AMPLIFICATION NEXT
MON-WED. THIS EVOLUTION/PROGRESSION WILL MOST LIKELY LEAD TO
STEADY EROSION OF INITIALLY STRONG RIDGING ALONG/OFFSHORE THE EAST
COAST FOLLOWED BY A SHIFT OF RIDGE EMPHASIS INTO THE GULF OF
MEXICO AND THEN SOME REBUILDING OF A RIDGE OVER THE EAST-CENTRAL
U.S. BY MIDWEEK AS WESTERN TROUGHING AMPLIFIES.
...MODEL GUIDANCE/UNCERTAINTY ASSESSMENT/PREFERENCES...
ONE SIGNIFICANT FOCUS OF THE FORECAST WILL BE ON THE STORM SYSTEM
ASSOCIATED WITH THE SHORTWAVE EMERGING FROM THE ROCKIES/HIGH
PLAINS AT THE START OF THE PERIOD EARLY SAT. THERE IS STILL A
MODERATE AMOUNT OF SPREAD FOR EXACTLY HOW THIS SYSTEM WILL EVOLVE
BUT MOST MODEL/ENSEMBLE SOLUTIONS HAVE TRENDED NOTICEABLY DEEPER
VERSUS 24 HOURS AGO, WHILE THE GFS CONTINUES TO BE THE DEEPEST
MODEL. THIS DEEPER TREND WOULD MERIT SOME INCORPORATION OF THE
00Z/06Z GFS SCENARIO INTO THE FORECAST AS PART OF A MODEL
COMPROMISE BUT OCCASIONALLY DEEP BIASES STILL LEAVE SOME LINGERING
DOUBT IN GOING AS DEEP AS THE GFS. THERE ARE STILL INDICATIONS
THAT A WEAK WAVE WILL FORM OFF THE NORTHEAST COAST AS THE PARENT
LOW TRACKS OVER SOUTHEAST CANADA. SPECIFICS OF THIS WAVE WILL
PLAY AN IMPORTANT ROLE IN HOW LONG COOL AIR REMAINS OVER NEW
ENGLAND.
THERE IS DECENT CONTINUITY FROM YESTERDAY THAT A TRAILING
SHORTWAVE REACHING THE NORTHWEST DURING THE WEEKEND SHOULD BE
FAIRLY WEAK AND PROGRESSIVE, WITH AT MOST A MODEST SURFACE
REFLECTION AS THE FEATURE CONTINUES ACROSS LOWER 48.
THE OTHER MEANINGFUL UNCERTAINTY IN TODAY'S FORECAST INVOLVES
EASTERN PACIFIC/WESTERN U.S. EVOLUTION TOWARD THE LATTER HALF OF
THE PERIOD, WITH MODELS AND TO A GREATER EXTENT INDIVIDUAL
ENSEMBLE MEMBERS DISPLAYING BROADENING SPREAD FOR COMBINED
EVOLUTION OF TROUGH ENERGY DIGGING INTO THE WEST AND
UPSTREAM/INFLUENCING ENERGY REACHING THE NORTHEAST PACIFIC. BEST
MODEL/MEAN CONSENSUS (ECMWF/CMC AND GEFS/ECMWF/CMC MEANS) HAS A
FAIRLY SHARP AND DEEP UPPER TROUGH REACHING JUST INLAND FROM THE
WEST COAST BY DAYS 6-7 TUE-WED, WITH INDICATIONS THAT THERE COULD
BE AN EMBEDDED CLOSED LOW. THIS MAJORITY SOLUTION IS A LITTLE
FASTER THAN THE 00Z GFS BUT SLOWER THAN THE 06Z RUN.
...WEATHER HIGHLIGHTS/THREATS...
THE DEEPENING STORM SYSTEM TRACKING FROM NEAR THE CENTRAL PLAINS
THROUGH THE GREAT LAKES INTO SOUTHEAST CANADA DURING THE WEEKEND
WILL BRING A BROAD AREA OF ACTIVE WEATHER TO THE CENTRAL AND
EASTERN U.S. AHEAD OF THE FRONT TRAILING FROM THE SURFACE LOW,
EXPECT AREAS OF HEAVY RAINFALL INCLUDING OVER PORTIONS OF THE
MS/OH VALLEY REGION THAT HAS ALREADY EXPERIENCED
CONSIDERABLE/EXCESSIVE RAINFALL. THUS FLOODING CONCERNS WILL
CONTINUE. SOME CONVECTION MAY ALSO BE STRONG TO SEVERE WITH SPC
CURRENTLY HIGHLIGHTING SUCH POTENTIAL FROM EXTREME NORTHEAST TX
INTO WESTERN TN AND VICINITY. CONSULT LATEST SPC OUTLOOKS FOR
LATEST INFO. MEANWHILE BEST POTENTIAL FOR COLD SECTOR SNOW WILL
EXTEND FROM THE NORTH-CENTRAL PLAINS THROUGH THE UPPER MS
VALLEY/UPPER GREAT LAKES AND INTO NEW ENGLAND, WITH A TRANSITION
ZONE/CHANGEOVER POSSIBLE BETWEEN THE SNOW AND RAIN AREAS. STRONG
WINDS MAY ALSO BECOME A CONCERN DEPENDING ON HOW THE SYSTEM
DEVELOPS. AFTER SYSTEM PASSAGE RAINFALL OF VARYING INTENSITY MAY
LINGER FOR A TIME OVER THE SOUTHERN TIER/SOUTHERN MID ATLANTIC.
OVER THE WEST, INITIALLY EXPECT SOME COASTAL/LOW ELEVATION RAIN
AND OTHERWISE SNOW FROM THE PACIFIC NORTHWEST/NORTHERN ROCKIES
INTO THE GREAT BASIN/SOUTH-CENTRAL ROCKIES FOLLOWED BY ANOTHER
PERIOD OF PRECIP THAT SHOULD EVENTUALLY PUSH SOUTHWARD FROM
NORTHERN AREAS INTO THE GREAT BASIN AND CA. GUIDANCE SPREAD FOR
DETAILS ALOFT IS STILL SUFFICIENTLY HIGH TO TEMPER CONFIDENCE IN
DETERMINING COVERAGE AND INTENSITY OF ACTIVITY OVER CA/GREAT
BASIN. HOWEVER THERE IS ENOUGH AGREEMENT IN PRINCIPLE THAT UPPER
TROUGH DEPTH MAY SUPPORT FAIRLY LOW SNOW LEVELS OVER SOME AREAS BY
NEXT MON-WED.
THE AMPLIFIED PATTERN WILL MAINTAIN A SHARP CONTRAST IN
TEMPERATURE ANOMALIES OVER THE LOWER 48. DURING THE WEEKEND SOME
AREAS IN THE EAST MAY SEE MINS OF 20-30F ABOVE NORMAL FOR
POTENTIAL DAILY RECORDS AND DAYTIME HIGHS 15-20F ABOVE NORMAL.
LESS EXTREME WARM ANOMALIES SHOULD PERSIST OVER THE EAST INTO NEXT
WEEK. ON THE OTHER HAND MUCH OF THE WEST INTO THE NORTHERN PLAINS
SHOULD REMAIN WELL BELOW NORMAL DURING THE FORECAST PERIOD. THE
NORTHERN HIGH PLAINS SHOULD BE COLDEST WITH MAX TEMPS AVERAGING
15-20F BELOW NORMAL BUT MANY OTHER LOCATIONS OVER THE
WEST/NORTHERN PLAINS SHOULD SEE ONE OR MORE DAYS WITH MIN AND/OR
MAX TEMPS AT LEAST 10F BELOW NORMAL AS WELL.
RAUSCH